Conventionally, microphone units are employed in voice input devices such as voice communication devices including mobile telephones and transceivers, information processing systems that employ techniques for analyzing inputted voice such as voice authentication systems, and recording devices. Recent years have seen a continuation in the miniaturization of electronic devices, and the development of microphone units that achieve smaller and thinner sizes is in full swing.
MEMS (Micro Electro Mechanical System) microphone devices that are created using semiconductor manufacturing techniques are known as microphone units that achieve smaller and thinner sizes (for example, see Patent Documents 1 through 3). Here, an example of the configuration of a conventional microphone unit will be described.
FIG. 13 is a schematic cross-sectional view illustrating an example of the configuration of a conventional microphone unit. As illustrated in FIG. 13, the conventional microphone unit 100 includes an MEMS chip 101 that converts an inputted sound wave into an electric signal, a substrate 102 on which the MEMS chip 101 is mounted, and a shield case 103 that covers the MEMS chip 101. A sound hole 103a for inputting a sound wave from the exterior is formed in the shield case 103.
A bottom end 103b of the shield case 103 is electrically connected to a grounding circuit pattern (not shown) formed in the substrate 102. Through this, the shield case 103 can shield the microphone unit 100 from electromagnetic noise.